I. Field
The following description relates generally to wireless communications, and more particularly to throttling transmit power in a Wireless Wide Area Network (WWAN) device utilizing thermal input in a wireless communication system.
II. Background
Wireless communication systems are widely deployed to provide various types of communication; for instance, voice and/or data can be provided via such wireless communication systems. A typical wireless communication system, or network, can provide multiple users access to one or more shared resources (e.g., bandwidth, transmit power, . . . ). For instance, a system can use a variety of multiple access techniques such as Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), Code Division Multiplexing (CDM), Orthogonal Frequency Division Multiplexing (OFDM), and others.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple access terminals. Each access terminal can communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to access terminals, and the reverse link (or uplink) refers to the communication link from access terminals to base stations. This communication link can be established via a single-in-single-out, multiple-in-single-out or a multiple-in-multiple-out (MIMO) system.
MIMO systems commonly employ multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas can be decomposed into NS independent channels, which can be referred to as spatial channels, where NS≦{NT, NR}. Each of the NS independent channels corresponds to a dimension. Moreover, MIMO systems can provide improved performance (e.g., increased spectral efficiency, higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.
MIMO systems can support various duplexing techniques to divide forward and reverse link communications over a common physical medium. For instance, frequency division duplex (FDD) systems can utilize disparate frequency regions for forward and reverse link communications. Further, in time division duplex (TDD) systems, forward and reverse link communications can employ a common frequency region so that the reciprocity principle allows estimation of the forward link channel from reverse link channel.
Wireless communication systems oftentimes employ one or more base stations that provide a coverage area. A typical base station can transmit multiple data streams for broadcast, multicast and/or unicast services, wherein a data stream may be a stream of data that can be of independent reception interest to an access terminal. An access terminal within the coverage area of such base station can be employed to receive one, more than one, or all the data streams carried by the composite stream. Likewise, an access terminal can transmit data to the base station or another access terminal.
According to an example, an access terminal can be a Wireless Wide Area Network (WWAN) device (e.g., WWAN module, . . . ) employed in conjunction with a computing device (e.g., notebook computer, handheld computer, personal digital assistant (PDA), . . . ). For instance, the WWAN device can be embedded in, removeably connectable to, etc. the computing device. However, the WWAN device can cause an overall ambient temperature of the computing device to rise (e.g., to a temperature level that detrimentally impacts performance of the computing device, one or more components associated with the computing device, and/or the WWAN device, . . . ). By way of illustration, the computing device can be sensitive to an amount of thermal energy to which it is exposed (e.g., lifetime of each component of the computing device can be a function of hot and cold temperatures to which such component is exposed, . . . ).
Changes in ambient temperature of the computing device can result from WWAN device operation. For example, increase in temperature can be caused by heat generated by a power amplifier on the WWAN device when transmitting data. Further, increase in temperature can result (e.g., to a lesser extent as compared to utilization of the power amplifier, . . . ) from heat generated by baseband processing of high speed data being downloaded by the WWAN device.
Conventional techniques typically fail to adequately account for the rise in temperature resulting from operation of WWAN devices. For instance, a common technique can include having WWAN devices operate in a manner similar to Wireless Local Area Network (WLAN) devices, where transmit power can be unilaterally reduced by the device itself when the temperature exceeds a threshold. However, unlike WWAN, WLAN base stations do not attempt to control the WLAN transmit power output on a computing device. WLAN devices operate in the unlicensed spectrum where behavior is much less regulated as compared to the licensed spectrum (e.g., in which WWAN devices operate, . . . ). Moreover, WWAN devices typically need to be qualified by global network operators to operate on their respective networks; to be qualified, WWAN devices commonly need to have transmission characteristics that meet requirements set by the global network operators. Thus, for example, the network typically governs transmit power employed by WWAN devices, which runs counter to allowing such devices to unilaterally alter their corresponding transmit power employed.